Tina, I'm asthmatic, overweight and only started running again in October last year. Yesterday, I finished my first half-marathon! I use a symbicort and ventalin inhaler daily.
I always take my ventalin inhaler with me and used it a lot initially, but probably more as a comfort item rather than out of actual need. What I found initially is that I was worrying too much about my asthma, which would lead to a tight chest. As time progressed, I learned to relax a bit more and had less and less tight chests.
I now have two puffs of ventalin before a run and not worry about it again throughout a whole run. I've found I'm now more in tune with my asthma than ever before.